Slotted cylindrical antenna



I N VEN TBS Jan.5,l954 c.E.sMn+lETAL SLOTTED CYLINDRICAL ANTENNA Filed oct. 1e, 1947 4 Sheets-Sheet 1 wl i.

Jan. 5, 1954 Filed Oct. 16, 1947 C. E. SMITH IAL SLOTTED CYLINDRICAL ANTENNA 4 Sheets-Sheet 2 SP/V f Jso J,as w V w 5 10 lol 10 Fre. I]

. INVENTORS QM Jan. 5, 1954 c. E. SMITH ETAL SLOTTED CYLINDRICAL ANTENNA 4 Sheets-Sheet 3 FIG. 15

Filed oct. 16, 1947 FIG. 12

IN VEN TOIZS MMM@ @Mx i. BY

Jan. 5, 1954. c. E. SMITH ErAL 2,665,381

SLOTTED CYLINDRICAL ANTENNA Filed oct. 1e, 1947 4 Sheets-Sheet 4 FG. I9

IN V EN TORS Patented Jan. 5, 1954 SLOTTED ,CYLINDRICAL yANTENN A Carl E. Smith, Cleveland, hio,and GeorgeSinclair, Toronto, Ontario, Canada, assignors, by mesne assignments, of one-half tosaidrSmith and one-halfto United Broadcasting Company,`

a corporationA of I Ohio Application October 16, 1947', Se1ialN0.'780,264

7 Claims;

The invention relates in general to antennas for usel with electromagnetic wave energy, and more particularly to conduits or hol-low cylinders hav--y ing'slots therein for the radiation of therradiant energy waves.

An object of the invention is to Aprovide an an tenna having a high gain in the horizontal plane, with low wind resistance andwith greater flexibility of control of the horizontal field intensity pattern for a given number of feed lines than is possible with'normal dipoles.V

Another object of the invention is to provide an antenna having a uniformfgain in the horizontal plane and which is capable of being vertically stacked to increase the-gain in the horizontal plane.

Another object of the invention is to provide an antenna to radiate circularlypolarized electromagnetic waves with* the `horizontal eld intensity pattern highly controllable as to nulls and/or circularity.

A further object of the invention is to provide a hollow `cylindrical antenna having a spiral slot l for eiiecting radiation of electromagnetic waves 25 having both horizontal and vertical components.`

A further object of the invention is tov provide a hollow cylindrical antenna having two symmetricallyplaced vertical slots anda horizontal slot, with the vertical slots fed 90 out of phase relative to the horizontal slot, to effect circular polarization of the radiated electromagnetic wave with a high uniform Vgain in the horizontal plane.

A still further object of the invention is to 4provide a hollow cylindrical 'antenna having two non. f

symmetrically placed slots such that the horizontal eld intensity pattern of .the horizontally polarized wave is not symmetrical about any line in the horizontal plane.

Another object of the invention is .to provide lips on the slots of a slotted cylindricalantenna:

to increase the capacity across thoserslots.

Another object of the invention is to 4provide capacity' lips on the .slots of slotted cylindrical antennas to affect the lradiation'rpattern of the 5 the 1i-n e 2o; 20 of Figure ,19;

radiated wave.

A still further object of the invention is to pro-- videinternal linsV attached. to the edges of the slots of a slotted cylindrical antenna` to increase the dimensions of the cavity behind the slot.

@ther objects anda fuller understandingof the invention may be had by referring to the following descriptionand claims, taken in Vconjunction withthe accompanying drawing, invwhich:v`

Figurev 1 is a developed view of the .preferred embodiment of the invention;

2 Figure 2 is a front elevational View of the preferred embodimentfof 'the invention;

Figures and 4 are cross-sectional views taken s along the lines 3`3 and 4 4 of Figure 2;

Figure 5 is a perspective view of an antenna similar to the preferred embodiment, but with a dilerent method of feeding;

Figure 6fisa cross-sectional view taken along lo* the `line G+S of Figuren;

Figure 7 isa perspective view of'a hollow cylindrical antenna having two symmetrical vertical slots for radiating horizontal-ly polarized electromagnetic waves;

Figure 8 "is a crossesectional View taken along 'theline 8-8 ofFgure 7;

Figure 9 is a'perspectiveview of another antenna having two non-symmetrically vplaced vertical slots;

,t Figurelo isa cross-sectional view taken along the line lll-I0 of Figure 9;

Figure 11 isa graph showing the field intensity pattern in the horizontal plane 'obtainable from theantenna of the gures 9 and 10;

Figure 12 is' a perspective view of a hollow cylindrical antenna having. a right and left hand spiral slot;

Figure 13. is a cross-sectional elevational view taken along the line |3QI3 of Figure 12;

Figure 14 is a cross-sectional view taken along 30 the line l4-l4 of Figure 12;

Figure 15 is a perspective view of a hollow cylindrical antenna having one spiral slot;

Figure 16 `is a cross-sectional -vieW taken along the line |6 |6 of Figure 15;

435 Figure 17 is a'fragmentary perspective view of a cylindrical rantenna having inwardly turned lips on the -vertical.slots;V

Figure 18- is a `cross-sectional view taken along thev line- I 8 I8 of Figure 17';

Figure 19 isa perspective' view of an antenna having capacity disks' fastened to the edges of the horizontal l gap of the antenna;

Figure -20 is a cross-sectional view taken along Figure 21r is'a perspective view of an antenna similar'to that shown vin Figure 5but including outwardly' turned lips on the vertical slots vand capacity disks on `thehorizcntal gap;

Figure 22 vis a cross-sectionalview taken along increase the cavity depth behind the slot.

The invention deals with antennas that have a slot or slots in a conduit, which conduit has been shown in the drawings and is preferably in the form of a hollow cylinder for the sake of symmetry. For further modifications of the invention, reference may be had to the co-pending application led concurrently herewith, entitled Three Slot Cylindrical Antenna, Serial No. 780,265. The preferred embodiment of the invention is shown in the Figures 1 to 4, and shows a hollow cylindrical antenna having an upper section 2| and a lower section 22 adapted to be supported by a mast 23. The Figure l is a developed view showing the hollow cylindrical upper and lower sections 2| and 22 slit open and laid into a fiat sheet in order to more clearly show the connections. The upper section 2| has first and second edges 24 and 25 for defining a first slot 33, and third and fourth edges 2G and 21 for defining a second slot 34. The first and second slots 33 and 34 are symmetrically placed about the periphery of the cylindrical upper section 2|, and are axially aligned with the mast 23. In a similar manner the lower section 22 has fifth and sixth edges 23 and 29 defining a third slot 35, and seventh and eighth edges 30 and 3| for defining a fourth slot 33. The third and fourth slots 35 and 36 are vertical and axially aligned with the mast 23, and are symmetrically spaced on the periphery of the lower section 22. The third and fourth slots 35 and 36 are spaced adjacent the first and second slots 33 and 34 on the upper section 2|. The first, second, third and fourth slots, 33, 34, 35 and 33, serve as the means to radiate the electromagnetic waves, and in this preferred embodiment of this invention are made a half-wave length long relative to the wave length of the electromagnetic wave. The upper and lower sections 2| and 22 are separated to form a horizontal gap 55 therebetween and are fastened to the mast 23 at a point where the potential to the glOuIlded mast is a minimum. Such points are found at the geometrical center of the periphery of the upper and lower sections between adjacent slots. Arms 32 are used to iixedly fasten the upper and lower sections 2| and 22 to the mast 23 at such points of minimum potential difference. Shorting bars 54 are used to close the ends of the vertical slots 33, 34, 35 and 36 adjacent the horizontal gap 55. voltage minimum point, since they are a quarter wave length distant from the feed point of the slots.

First, second, third and fourth axially aligned parallel conductors 31, 38, 39 and 40 are provided I,

within the mast 23 to connect the antenna to some electrical device, such as a transmitter so that the antenna may radiate wave energy, or it may be a receiver such that the antenna may be receptive to such wave energy. The first and second conductors 31 and 38 are adapted to feed the first, second, third and fourth vertical slots, 33, 34, 35 and 35, and the third and fourth conductors 39 and 4|! are adapted to feed the horizontal gap 55. By energizing the vertical slots, horizontal polarization of the radiated wave is effected, and by energizing the upper section against the lower section 22 vertical polarization of the radiated wave is effected. By establishing these two planes of radiation in 90 time phase displacement, elliptical polarization of the radiated wave is effected. By so making the amplitude of the horizontal and vertical components equal, the elliptically polarized wave becomes circularly polarized. The upper and lower sections These are not essential, but are at a 2| and 22 that effect vertically polarized radiation establish a substantially circular field intensity pattern in the horizontal plane since it is akin to a fat dipole. The vertical slots in the upper and lower sections 2| and 22 radiate horizontally polarized electromagnetic waves with the field intensity pattern in the horizontal plane substantially circular. The result of the combination of the circular horizontal eld intensity patterns of both the vertically and horizontally polarized waves gives a substantially uniform gain in the horizontal plane with a substantially circularly polarized electromagnetic wave.

The first and second conductors, 31 and 38, are connected to the vertical slots by short feeder lines. The first conductor 31 is connected to the slot edge 24 by a feeder 42, and is connected to the diametrically opposite slot edge 26 by a feeder 44. The second conductor 38 is connected to the slot edge 25 by a feeder 43 and is also connected to the diametrically opposite slot edge 21 by the feeder 45. These feed connections are at the center of the first and second slots 33 and 34 in the upper section 2 I. The same first and second conductors 31 and 38 feed the third and fourth slots 35 and 36 in the lower section 22, the feed point for these slots being at the center thereof, which is substantially one-half wave length below the feed point for the first and second slots, 33 and 34. Since the feed point for the vertical slots in the lower section 22 is onehalf the wave length distant from the feed point of the vertical slots in the upper section 2|, the feeding connections are reversed in order to make the polarity of the waves emanating from the first and third slots 33 and 35 reinforce rather than oppose each other. The same is true of the waves emanating from the second and fourth slots 34 and 36. To feed the third and fourth slots, the first conductor 31 is connected to the slot edge 3| by the feeder 48 and is connected to the diametrically opposite slot edge 29 by the feeder 46. The second conductor 38 is connected to the slot edge 3E) by the feeder 49 and is also connected to the diametrically opposite slot edge 28 by the feeder 41.

The third and fourth conductors are adapted to energize the upper section 2| against the lower section 22 by feeding across the gap 55. Two diametrically opposite feed points on the gap have been chosen, with the third conductor 39 connected to one point on the upper section 2| by the feeder 50, and connected to a diametrically opposite point on the upper section 2| by the feeder 5|. The fourth conductor 40 is in a similar fashion connected to diametrically opposite feed points on the lower section 22 by feeders 52 and 53.

The antenna shown in Figures 1 to 4, inclusive, which is the preferred embodiment of the invention, may be considered as a transducer, as it efficiently transfers energy between free space and an electrical device such as a radio transmitter or receiver. This antenna produces a horizontal field intensity pattern that may be made very nearly circular and hence the gain in the horizontal plane will be substantially uniform. The antenna in its preferred form has a diameter which is only a fraction of a wave length, in the order of 1/8 a wave length, and hence to use this antenna in the V. H. F. band the diameter will be physically small enough so that the entire antenna will have a low wind resistance. The antenna is a complete entity and needs no ground plane. The

result vbeinge thainthis `*antenna-.xlsrfcapablerof bes: ing: s.vertictl-lykstaakt-idv infamy; j plurality. of. I'an-f i tennas suchfas-=two;.=..four.orreight or'any. otherl number .toz'wfflatterr V.the ".rtoroidalf `pattern and hence increase'the. :gain in thezhorizonta'l plane.

The 'slots .may` bex-ofzfanya practical width' and:` inrpracticei y*areifma'de ."sufliciently. .wide inl order tog develop the. 'necessary potential difference thereacross 'without arcing. The` :slot width is also suicienteto rprevent icingor bridging across the. slot by Asleetformation which: 'would f shorty the slot;-

Figure shows yanotheifform of. antenna .which is :quite 4similar-.tozltlieapreferred embodiment of the invention. in that f theiupper and lower: sections 2 l and 22- stillcontain-...first-f second; third andfourthyertical .slots-331.34; 35v and-36, and form-aJ 'horizontal gap155-vftherebetween,` .The method of..feedingmhe-rantenna' shownein Fig.- ures5 and 1.6 .hasbeenfaccomplished in e, differenltf manner howeven; with first; and.- second.- co. axialA cables 4EU'ancl--Gh eachiserving -to energize Vboth therfverticall .slots andy `the-:horizontal gap 55. The: mast-orfmeans 1tofsupportthe. antenne, shown in Figures-5 and V6 has not been shown for thexsake of clarity .in the drawing, but. it is tobeunderstood' that this antenna may bev supported ina fashion similar to the method of supportingthe.preferred.embodiment of the inventionl The shorting .bars 54 which were used in thepreferredembodiment of the inven-l tion to close. thewends of. the verticalxslotsadjacent to thehorizontalgap 55 have been removed in the antennarshown in the Figures 5 and'. The first coaxial cable 611|V is shown as beingaxiallyV aligned `wi-ththe axis of the an tenna and close to the axisthereof in a position suchV as it would maintain were a .mast physi cally present to support the antenna.` Since thek coaxial cable method ofv feeding is an unbalanced'form of feeding withrespect to-ground, the coaxial cable has been electrically connect'- ed to the inside. of .thewlower section 22 at a point at least a quarter-wave distance fromthe feed point. To accomplish this, the coaxial cable 6i! has been turned at right. angles to its axially aligned directionand extended horizontally outward to the interior wall of the lower section .22 and contactsl this `interior wall at a point B2". From this point `S2 the coaxialcable Sll'extends.peripherally:around and upward tothe...inte`rsection .56 of .the horizontal gap 55` with'v the` .second .and fourth slots `34 and 36... The. outer shellfof the coaxialcable Si! terminates atthepoint 66 of this. intersection, and the center conductor of extendsacross and .connects to the diagonally. opposite corner el' of this intersection 5t. The second coaxial cable .6l is turned r.horizontally andA extends outward to the `inner surface of the lower section 22 at a point 63', from'whence it turns'. and continues peripherally .around and ucward along the `lower section 22 lto reach the second intersectionf. ofthe horizontal gap-55 and 'the first". and third. Ih` outer shellfof the.. nat'es at the point EG of.

.coaxial cable 5I termif this intersection?, and. the" inner conductor of .the coaxial cable 6l extends .across to connect to thediagonally opposite, corner 65 "of this intersectiont'l. The line joninglthe points?. andf'l3l isnormalto the plane .extending through .the vertical. slotsso that symmetry in .the feeding of the antenna is: maintained.`

vIlile eifect of .feeding..diagonally .across theY the coaxial cable 69- verticalslots 33 and 35;

intersectionsucand f tromagneti-c.v radiated tical".` .andA horizontal. tennafis .capableaoftproducing eld'` izontally polarized waves;-

The Figures# and 8 two #vertical slotsfor the. establishment ofi horizontally ,polarizedelectromagnetic Waves.. which 1 may-have. -a substantially circulary field` intensity pattern in. the horizontal.. plane.v 'H has-rst and second edges The .cylinder lil vand `the vsecondarie fourth edges 'I3 and 151- are diametrically vopposite eachother.

secondconductors ing axially aligned are `.spaced f relativelyclose together in :relation to Etheir spacing from. the cylinder 'Il to approx"- imate their positiontwere a mast or port to-bedepicted within thecylinder 1i. Su'ch a mast or. support has beenV omitted fromfithei- Figures 7 and 8 to more clearly vshow the cone'V The first. conductor 16 is arranged to'be'fconnected to the. rst .and third edges. .J2 and 'I4' by feeders 18 andls respectively,.and th'evsecond conductor` nections of the feeding arrangement.`

il is arranged to be connected to the secondfand fourth edges 13 and 'I5 by feeders'v fspectively.

Sinceboth slots'Z aids the radiation posing such radiation. rlhe amplitudes of the ra-v diation from `each slot are substantially equal, and hence the horizontal field intensity' pattern of ho rizontallv` polarized wave is substantially circu-Y lar, The firstandsecond slots '.82 and 83 have been shown as approximately a half 'wave length long, which isa lsatisfactory length for-the radiation ofpower, however the` effective full wave length in length if vdesired sim-v ilar to those-shown in Figure 5.

The Figures 9 and 10 show a still further'modication ofthe. invention wherein'a cylinder 3l hastwo non-symmetrically placed slots lto produce. horizontally polarized waves wherein'the horizontal .eld intensity pattern is non-sym'- metrical about an axis inthe horizontalplane. The cylinders?. land. 89 .for definingv a rlrst.v vertical slot 92,.and thirdl and fourth edges. Btavsecond vertical slot 93.

der .Q'fand are `spaced 90 physical degrees apart about the periphery of the cylinder 81. First andlsecond conductors S4 rst. and second feeders H10' and.l lill respectively..Y

By using .two separate pairv to. feed each of the -two :vertioalfslots 92 and 93,'.amuch greater degree of control. over" the horizontal eld'intensity `'pattern is. achieved. Variations inlmagnitude and phase may-easily be accomplished to changer the shapeE ofthe hori-r 51 is f. .itozfproducef Yen; elecr-l .wave thatrhas 1 both: a were? component'. Suchian anar nlerlsityipatterne'. in '.theznhorizontal;` plane.. .-sthat" Varel very nearly: circular.. for :both fthe vertically and. hor--v show l a further. modifica-5 tion fofethevinvention wherein a cylinder Il has.

12 and foridefpning: a rst verticaluslot 82, andthirdiand.v

Frstand.: 1-6 and -.1'l are. shown '-asbef within the ycylinder ll, and

Some SUD- and .8 l' re'-A andt arefed from the sameV pair of conductors, the ra'diatedfield of eaoh'slot'.

from the other, rather than 'op-z slots may be-madean` has-first and-second edgess'88 1 andA 9| fory defining.. The first. and secondv slotsl92 and-93.. are axially. alignedv with the. cylin-1 and 1'95 fare connected: to the-.rst andy-second slot edges-90 and 9| by 98 land '99 respectivelyj. and third and fourth. conductors .96 yand 91 are. connectedto .the slot. edges 88- and 89- by :feeders pairs of conductors., one

7 eters to vary to control the eld intensity pattern in the horizontal plane. These four parameters are relative magnitude, relative electrical phase, the diameter of the cylindrical antenna in wave lengths, and the peripheral spacing of the slots upon the cylindrical antenna. The graphV of Figure 11 shows a horizontal field intensity pattern which the antenna of Figures 9 and 10 is capable of producing. The horizontal field intensity pattern shown in Figure 11 was produced by actual measurements by an antenna similar to that shown in Figures 9 and 10, wherein two vertical slots are spaced 90 apart on the periphery of the cylinder. The first slot was oriented at the radial, and the second slot was oriented at the 270 radial. The diameter of the cylinder was established at one-half wave length, and the feeding was such that the second slot was fed with a magnitude of voltage one-half the magnitude of voltage applied to the first slot, and with the second slot fed 90 electrical degrees advanced in phase.

Figures 12, 13 and 14 show a still further modification of the invention wherein two oppositely rotating spiral slots are fashioned in a hollow cylinder |08. The cylinder |08 is shown as being supported by a mast |09, and is fastened to the mast |09 by supports IIO. First and second edges ||I and |I2 dene a first slot ||5, which is a left-hand spiral spot. Third and fourth edges II3 and ||4 dene a second slot IIE, which is a right-hand spiral slot. The first and second spiral slots I I5 and IIB are each made one wave length long, and each is inclined 45 to the axis of the cylinder |08. The diameter of the cylinder |08 has been chosen such that each slot ||5 and IIB makes one complete revolution about the periphery of the cylinder |08. The supports ||0 that fasten the cylinder |08 to the mast |09, are placed at a voltage minimum point of the antenna, which voltage minimum point is produced at points equi-distant from the various slot edges. There are four such points in the antenna as shown in the Figures 12, 13 and 14, and the supports I I0 have been located at such voltage minimum points. First and second coaxial cables I I'I and I8 are used to feed the iirst and second slots I5 and I I6. These rst and second coaxial cables II'I and I|8 have been omitted from the perspective view of Figure l2 for the sake of clarity in this view. The first coaxial cable |I'I extends through a hole ||9 in the mast |09 at a point adjacent to one of the supports ||0, and electrically contacts the inner surface of the cylinder |08 at this point. The rst coaxial cable then extends upwardly to reach the midpoint |08 of the iirst spiral slot ||5. The outer shell of the coaxial cable ||1 ends at the second edge H2, and the inner conductor of the coaxial cable II extends across the slot I|5 to connect to the first edge I I I. A second coaxial cable I8 extends through a hole |20 in the mast |09 adj acent 'to a support ||0 and connects to the inner surface of the cylinder |08. From this point adjacent the support I|0 the coaxial cable |I8 extends upward vertically to reach the mid-point |01 of the second slot II6. The outer shell of the coaxial cable I I8 ends at the fourth edge I I4, and the inner conductor of the coaxial cable I8 extends across the second slot ||6 to connect to the third edge IIS at the mid-point |01.

The first and second slots I|5 and IIE each have a horizontal component and a vertical component, and hence the electromagnetic wave emanating from the spiral slots have both vertical and horizontal components. The horizontal field intensity patterns of both the horizontal and vertically polarized electromagnetic waves of this antenna are very nearly circular.

The antenna shown in Figures 15 and 16 is a simplified version of the antenna shown in Figures 12, 13 and 14, inasmuch as the antenna comprises a cylinder |22 having only one spiral slot. First and second edges |23 and |24 define a slot |25 which has been shown as a left-hand spiral slot. Slot |25 makes a 45 angle with the axis of the cylinder |22. The length of the slot |25 has been made equivalent to one wave length, and the diameter of the cylinder |22 has been chosen such that the slot |25 will complete one revolution about the periphery of the cylinder |22. A coaxial cable |26 is used to feed the slot |25, and is shown as being fastened to the inner surface of the cylinder |22 and axially aligned therewith. The outer shell of the coaxial cable |26 ends at the mid-point I2| of the slot edge |24, and the inner conductor of the coaxial cable |26 extends across the slot |25 to connect to the edge |23 at the mid-point I2I. A novel feature of the antenna shown in Figures 15 and 16 is that the cylinder |22 needs no separate support, the cylinder |22 may support itself. The slot |25 in the cylinder |22 simulates a slot formed in a hollow flag pole like structure.

Satisfactory radiation may be obtained from the antenna shown in Figures 15 and 16, and substantially circular horizontal field intensity patterns of both the horizontal and vertically polarized waves may be attained.

The slot |25 in the cylinder |22 of Figures 15 and 16 may have some form of insulator across this slot to strengthen the entire antenna structure. Such an insulator may be a conduit insulator covering the entire slot or may be one or more segments extending across at any plurality of points on the slot |25. Likewise insulators may be placed across the slots ||5 and II6 in the antenna shown in Figures 12, 13 and 14.

The antenna shown in Figures 17 and 18 shows a fragment of a two slot cylindrical antenna wherein inwardly turned lips |28 are provided on the Vertical slot |29 to increase the capacity across this vertical slot. By increasing the capacity across the vertical slots, the impedance across the slot is changed and hence such lips may be used to obtain a correct impedance match between the transmission line and the slots in the cylinder. By experiment, it has been found that the size or effective area of these lips is the controlling factor so the result obtained therefrom is attributable to capacity.

The Figures 19 and 20 show a cylinder |30 having two vertical slots |3| and a horizontal gap |32. The horizontal gap |32 has been provided with capacity disks |33 which extend horizontally from the edges of the cylinder that form the horizontal gap |32. The capacity disks Y |33 are not continuous, each being formed substantially in halves so that the Vertical slots l|3I are not closed by the capacity disks |33. The

capacity 'disks |33 perform a function similarv to the lips |28 shown in Figures 1'7 and 18 in that they increase the capacity across the horizontal gap |32. By so increasing the capacity, the impedance is changed, and more energy is passed between the upper and lower sections of the cylindrical antenna |30. The antenna shown in Figures 19 and 20 is similar to `that shown yin` the preferred embodiment shown in Figures 1, 2, l'3 and 4 and is-similar to the modified form shown in Figures and v6. The antenna shown in Figures 5 and 6, since it is fed diagonally acrossthe juncture of the'horizontal gap and the vertical slot, depends upon equal impedance of `the vertical. slots. and horizontal gap to produce substantially equal Ihori.- zontal and 'vertical radiation. The capacity disks |33' have been used to advantage 'to2 in.- crease the horizontally lpolarized radiation, in that by increasing the capacity between 4the upper and lower sections of. the entire antenna, more energy is available across'` the vertical slots in both the upper. andlower sections, hence horizontal*radiation.is-increased.

Figures `21 and 22 show astilli further modification wherein outwardly turned lips '|34 are connected to the edges of the vertical slots |35 of the slotted cylindrical. antenna |36. Capacity disks |31 are connectedr to the edgesof a -horizontal gap |38 at thelongitudinal center of. the antenna |35. The lips |34 have been shown as outwardly turned rather than as inwardly turned such as the .lips |28 of Figure 17, to rillustrate that the capacity effect of the lips |34 is the prime factor, .and not `the direction of deflection. By combining the vertical lips |34 and the horizontal capacity disks |31 the impedance of both. vertical slot |35 and horizontal gap |38 may be changed to produce the correct impedance match desired in any particular application. 'Such changes of impedance may be utilized -to advantage with a feed system similar to that shown in the antenna of Figures 5and 6, wherein the feed vis diagonally across the juncture ofthe vertical slot and the horizontal gap.

As shown in Figures 21 and 22 the` capacity lips |3=i need not be made the same radial length as the radial length of the capacity disks i3?, the radial length of each determining `the effective area and hence the capacity desired to obtain the correct impedance match of the respective vertical slotor horizontal gap.

The Figure 23 shows a sectional view in per.- spective of a slotted cylindrical antenna `|42 being carried by a mast |43, by means of supports iii. Edges ll define two vertical slots |39. Fins lill are connected to each ofthe edges |40. and extend inwardly toward the mast |43 for approximately half the radial distance rbetween the antenna U22 proper and the masty |43, then deviate to extend peripherally around the mast |43 and substantially parallel therewith. The effect of the ns HH is to increase .the-dimensions of the cavity behind the vertical slot |39 since-the current iiows on the surfaceof theantenna |42, and the total surface is vincreased by the 4iin ldlbeing placed inside the cavity behind the slot |39.

The uns Mil are helpful to control the impedance of the slots 39 since they may be caused to produce standing waves on the surface of the antenna M2 and since they effectively increase the dimensions of the cavity in wave lengths without changing the diameter of the antenna ft2. By proper designing of the dimensions of the fins IGI, control of the driving point impedance may be effected.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combina- 10 tion and arrangement of parts may beresorted to without departing from the spirit andthe scope of the inventionv as hereinafter claimed.

l. A transducer ior 'transferring electromagnetic wave energy between freespace and an electrical device utilizing said electromagnetic waves, said transducer comprising electrically conducting conduit means, at least first and second substantially parallel edges in said conduit Vmeans for defining slot means therein,'said slot means having a narrow width relative to the length thereof, said slot means having a lengthwise'dimension with a component aligned parallel to the ci said conduit means, a single slot insaid slot means having alengthwise dimension With-a transverse component extending substantially completely around said conduit means, at least part of said conduit means deninga single dielectric-filledA cavity for said slot means and transmission line means connected across each slot in said slot means.

2. An antenna for circularly polarized electromagnetic waves of a given wave length with a substantially circular horizontal eld intensity pattern, said antenna comprising electrically conducting conduit means, means for mounting said conduit means with the axis thereof in a vertical position, first and Second substantially parallel edges in said conduit means for defining a first slot, thirdV and fourth substantially parallel edges in said conduit means for defining a second slotsaid slots `being substantially axially parallel and equally-spaced on the periphery of said conduit means, each of said slots having u `a length at least equal to a half of said given wave length, first feed means within the confines of said conduit means connected across at least the center of each of said slots, fifth and sixth substantiallyparallel edges in said conduit means for Vdefining a` third slot with the lengthwise dimension substantially extending about the periphery of said conduit means in a plane normal to the axis thereof, and second feed means within theconnes of said conduit means connested across the edges of said third slot.

3. An antenna for circularly polarized electromagnetic waves of a given wave length with a substantially circular `horizontal field intensity pattern, said antenna comprising electrically conducting conduit means, means for mounting said conduit means with the axis thereof in a vertical position, first and second substantially parallel edges in said conduit means for dening a rst slot, third and fourth substantially parallel edges in said conduit means for defining a second slot, said slots being substantially axially parallel and equally spaced on the periphery of said conduit means, each of said slots having a length at least-equal to a hajlf of said given wave length, first feed means within the confines of said conduit means connected across at least the center of the edges of each of said slots, fifth and sixth substantially parallel edges in said conduit means for defining a third slot with the lengthwise dimension substantially extending about the periphery of said conduit means in a plane normal to the axis thereof, second feed means within the confines of said conduit means connected across the edges of said third slot, said rst and second feed means including rst, second, third and fourth substantially parallel conductors substantially axially parallel with said conduit means, said rst feed means including first and second feeder lines extending substantially horizontally to connect the center of each of said first and third edges to said first conductor and third and fourth feeder lines to connect the center of each of said second and fourth edges to said second conductor, and said second feed means including fifth and sixth feeder lines extending substantially horizontally to connect said fifth and sixth edges to said third and fourth conductors, respectively.

4. An antenna for circularly polarized electromagnetic waves of a given Wave length with a. substantially circular horizontal f'leld intensity pattern, said antenna comprising electrically conducting conduit means, means for mounting said conduit means with the axis thereof in a vertical position, first and second substantially parallel edges in said conduit means for dening a first slot, third and fourth substantially parallel edges in said conduit means for defining a second slot, said slots being substantially axially parallel and equally spaced on the periphery of said conduit means, each of said slots having a length at least equal to a half of said given wave length, fifth and sixth substantially parallel edges in said conduit means for defining a third slot with the lengthwise dimension substantially extending about the periphery of said conduit means in a plane normal to the axis thereof, first and second feed means within the confines of said conduit means, said first and third slots defining a first juncture and said second and third slots defining a second juncture, said rst and second feed means including first and second coaxial cables, means for connecting the diagonally opposite corners of said rst juncture to the re spective two conductors of said first coaxial cable, and means for connecting the diagonally opposite corners of said second juncture to the respective two conductors of said second coaxial cable.

5. An antenna comprising electrically conducting conduit means having an axis, first and second substantially parallel edges in said conduit means for defining a first slot, third and fourth substantially parallel edges in said conduit means foi` defining a second slot, said slots being substantially axially parallel and equally spaced on the periphery of said conduit means, each of said slots having a length at least equal to a half of said given wave length, fifth and sixth substantially parallel edges in said conduit means for defining a third slot with the lengthwise dimension substantially extending about the periphery of said conduit means in a plane normal to the axis thereof, and transmission line means within the confines of said conduit means connected across the center of each of said first and second slots and connected across the edges of said third slot.

6. An antenna comprising electrically conducting conduit means having an axis, first and second substantially parallel edges in said conduit means for defining a rst axially parallel slot, said slot having a length at least equal to a half of said given Wave length, third and fourth substantially parallel edges in said conduit means for defining a second slot with the lengthwise dimension extending substantially completely around the periphery of said conduit means in a plane substantially normal to the axis thereof, and transmission line means Within the confines of said conduit means conected across the center of said first slot and connected across the edges of said second slot.

7. An antenna comprising electrically conducting conduit means having an axis, a plurality of substantially parallel edges in said conduit means for defining a plurality of slots, said slots being substantiallyaxially parallel and equally spaced on the periphery of said conduit means, each of said slots having a length at least equal to a half of said given wave length, additional substantially parallel edges in said conduit means for defining a transverse slot with the lengthwise dimension substantially extending about the periphery of said conduit means in a plane substantially normal to the axis thereof, and transmission line means within the confines of said conduit means connected across the center of each of said axially parallel slots and connected across the edges of said transverse slot.

CARL E. SMITH. GEORGE SINCLAIR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,129,712 Southworth Sept. 13, 1938 2,158,376 Moser et al May 16, 1939 2,234,293 Usselman Mar. 11, 1941 2,238,770 Blumlein Apr. 15, 1941 2,250,096 Engbert July 22, 1941 2,385,783 Alford et al. Oct. 2, 1945 2,404,196 Seeley July 16, 1946 2,405,242 Southworth Aug. 6, 1946 2,414,266 Lindenblad Jan. 14, 1947 2,415,094 Hansen et al Feb. 4, 1947 2,417,895 Wheeler Mar. 25, 1947 2,488,419 Lindenblad Nov. 15, 1949 2,511,029 Willoughby June 13, 1950 2,549,783 De Rosa Apr. 24, 1951 2,557,951 De Rosa June 26, 1951 OTHER REFERENCES Radio, July 1946, pages 14 and 15. F. M. & Television, September 1946, pages 45 f to 47. 

